The present invention concerns a waveguide, a process for the production of a waveguide, use of an intermediate layer on a waveguide and use of an organic substrate as a carrier substrate on a waveguide.
For many uses, for example sensors, integrated optics and the like it is desirable to have planar waveguides available. As shown in FIG. 1a such a waveguide, in its simplest form, includes a waveguide layer 1 with a refractive index nF on a substrate 2 with a refractive index nS and an ambient medium 3, the so-called cover medium, or cover, with a refractive index nC The cover medium can in turn be formed by a layer or a layer system, as shown in FIG. 1b. The following applies: nC<nF and nS<nF.
For many uses at least one of those layers must be structured. In order for light to be coupled at all into the waveguide, the method which is in fact the most elegant method involves providing the waveguide with a structure 4—a grating—as shown in FIG. 2a, and coupling the light 5, for example a laser beam, into the waveguide layer 1 by way of diffraction. If the coupling-in angle, grating period and waveguide layer thickness are suitably selected, the light 6 is propagated in the waveguide layer 1 with a given propagation mode and leaves the waveguide for example at an end face 7.
It is immaterial whether the grating 4 is provided at the substrate surface or in or at the waveguide layer.
In addition it is often desirable for the waveguide to be spatially structured as a whole. FIG. 1b shows a waveguide without spatial structuring, FIGS. 3 and 4 show structured strip-type waveguides and FIG. 5 shows a buried strip-type waveguide. FIGS. 6 and 7 are a plan view and a view in section purely by way of example of more complex spatial structures of a waveguide. Structured waveguides of that kind are widely used for example in the communications art or in the sensor art.
As waveguides of that kind are usually constructed on a glass substrate, the structuring procedures employed are photo-lithographic methods and the following etching methods: ion milling, reactive ion etching, wet-chemical etching and the like.
Such structuring procedures are time-consuming and expensive.
In addition waveguides on a glass substrate can only be shaped with difficulty and they are sensitive in regard to mechanical stresses such as impact stresses.
The substrate/waveguide layer/environment interaction but in particular the substrate/waveguide layer interaction which is relevant here substantially determines the waveguide property.